1. Field of the Invention
The present invention relates in general to a hydraulic cylinder, and more particularly, to a hydraulic cylinder suspension method for actively controlling vibration that is generated when a hydraulic cylinder such as a boom cylinder in a construction vehicle stops running all of a sudden.
2. Description of the Related Art
In general, a construction vehicle including an excavator is provided with various working equipments such as a boom, arm, and bucket, and is driven by a hydraulic cylinder that is operated by hydraulic fluid from a hydraulic pump. Also, a control valve is installed between the hydraulic pump and the hydraulic cylinder. It is the control valve that controls the hydraulic fluid from the hydraulic pump and supplies it to every hydraulic cylinder. More specifically, to drive the construction vehicle, a driver operates an operation lever, and then a control device controls the control valve, whereby hydraulic pressure, direction and flow of the hydraulic fluid supplied to the hydraulic cylinders are controlled.
The working equipment is usually heavy and massive capable of withstanding overload and rough work environment. Because of its heavy weight, inertia of the working equipment is also large. Thus, when the working equipment is in operation or stops running, it vibrates a lot due to the large inertia. In case of driving a construction vehicle, although an experienced driver can operate the operation lever with great delicacy and skill to move the working equipment gently, a beginner often finds difficulty in handling the operation lever, especially for starting and finishing the operation of the lever because of shock-induced vibration generated by inertia of the working equipment.
Moreover, sometimes drivers tend to move the operation lever quickly to finish work within time. When the operation lever is manipulated fast, the spool in the control valve for supplying hydraulic fluid to the hydraulic cylinder is moved violently. Therefore, vibration is generated due to shock at the start or end of the hydraulic cylinder, and repeatedly generated vibration makes drivers feel more tired.
As aforementioned, the vibration generated at the start or end of the operation of the working equipment adds to the fatigue of the drivers, which not only reduces work efficiency but also shortens lifespan of the vehicle. Thus, there have been a number of attempts to resolve the above problems.
One of generally used techniques for relieving shocks generated from a sudden operation of the working equipment is to use a pressure sensor that senses whether the operation lever starts operating suddenly and if so, a controller controls the control valve by changing an operation signal from the operation lever to proper signal for preventing vibration.
However, the above technique only attempts to control the control valve to prevent the sudden operation of the working equipment by changing the operation signal from the operation lever, and it does not provide a fundamental solution for the actual vibration that is generated when the hydraulic cylinder of the working equipment gets a shock.